1. Field of Invention
The invention relates to a vehicle navigation system and a recording medium which executes matching processing of present position detection information to road information, and provides route guidance.
2. Description of Related Art
Since traffic density, especially in the urban areas, has been increasing in recent years and surplus land space has been decreasing, a growing number of newly constructed roads have taken on a multilevel structure. Therefore, the position of a vehicle can be mistakenly identified when a navigation system provides navigation guidance in a case where a plurality of the roads run in parallel. For example, according to the highway recognition system proposed in Japanese Patent Publication No.137096/90, the related art discloses a system which starts to check the time when the system determines the velocity of the running vehicle is higher than a predetermined velocity, and determines the vehicle is running on a highway when the velocity lasts longer than a predetermined time. Further, the system according to the related art detects and cumulates the steering movements when the velocity of the vehicle is higher than the predetermined velocity, and determines whether the vehicle is running on the highway depending on whether the steering angle is larger than the predetermined value. Also the related art discloses a system which determines when the vehicle leaves the highway according to the condition that the velocity decreases as a direction indicator functions and the steering angle is larger than the predetermined value. (See Japanese Patent Publications Nos. 137097/90.about.137100/90).
The above mentioned related art device determines that the vehicle is running on the highway when the velocity of the vehicle lasts more than the predetermined time, however, according to recent traffic conditions, when the vehicle runs a main road although categorized as an ordinary road, the velocity of the vehicle can be very high depending on a road section. Therefore, the system can't determine simply by the velocity of the vehicle whether the road on which the vehicle is running is a highway. Further, the place where a highway and an ordinary road run in parallel with a two level structure and also the place where two ordinary roads or two highways run in parallel with a two level structure have been increasing. Under these conditions, the prior system can not determine the road on which the vehicle is running by the velocity of the vehicle.